In recent years various efforts have been exerted to supplant conventional aerosol-type dispensers, which used hydrocarbons such as isobutane, or fluorocarbons such as freon, with other propellant means. Such efforts were generally compelled by several factors, the substantial increase in petroleum prices, by scientists' concern in vented fluorocarbons destroying or seriously diminishing the protective ozone layer in the atmosphere which resulted in prohibitive federal and state legislations, and by the inherent explosive and flammable properties of conventional aerosols.
The developmental work took several directions, from the use of mechanical components such as springs, pistons and spring loaded valves; the use of compressed air and gaseous media other than hydrocarbons and fluorocarbons; as well as various types of packaged flexible and expandable inserts with self-contained gas generating components. The latter have shown greater promise both from economic and safety considerations as well as the simplicity and reliability of performance. The embodiments of the present invention disclosed hereinafter involve novel, useful and non-obvious improvements in such packaged inserts, and/or sequential pressure generating dispensing containers.